For years paleontologist have thought that Tyrannosaurus arms were small to compinsate for its gigantic skull. Its ancestors had long arms and it was thought that the arms shrunk throughout its evolution as it grew larger. However the recent discovery of Raptorex has challenged this theory. It evolved millions of years before Tyrannosaurus and had a realitivley small head but its arms were very tiny compared to its body size. If the "shrank as they gre" theory was correct and since the arms of Raptorex were so small then the arms would have been gone long before Tyrannosaurus came around. Why do you think Tyrannosaurus has susch small arms?